The present invention relates to a special effect apparatus, and particularly to a special effect apparatus which extends dimming effects and fading effects and realizes new effects.
Recently, it has been possible to view on, for example, television programs, signal processed video images which have been curved and wrapped around a background image, and being displayed so as to appear to have been pasted on paper, with this image then appearing to have been turned over in the way that a piece of paper would be turned over.
With this kind of free use of special effects, when a composite image is formed from a background picture and a signal processed picture (i.e. a foreground picture), this composite image is displayed by switching over between these two pictures in accordance with a key signal for inputting. This key signal is generated in accordance with the inputted key signal.
While this composite picture is being constructed, depth data is given, for example, to each of the picture elements, the depth data for the picture elements for the number of pictures which the image is to be composed of is compared, so that processing can then be carried out whereby the picture elements for, for example, the foreground are displayed and the picture elements for the background are concealed. This depth data (known as Z data) is then used for each of the other various special effects.
By using this kind of depth data, if the picture has depth, a dim effect whereby the picture darkens to a certain extent or a fading effect whereby the picture merges into the background can be obtained which can be utilized while the picture is being formed.
A special effects apparatus for carrying out the dim effect and fade effect in the prior art will now be described.
FIG. 1 shows a block diagram of the circuit for carrying out the prior art dim and fade effects. As shown FIG. 1, a signal G.sub.Z which varies between 0 and 1 is generated in the key signal by the G.sub.Z generator 41 using the depth data (Z data). This G.sub.Z signal is given by the following. EQU G.sub.Z =(Z-Z.sub.O).multidot.Z.sub.g ( 1)
For example, when a picture is being formed which will darken with depth, the key signal G.sub.z given by equation (1) is used. In equation (1), Z is the depth data, Z.sub.0 is a standard value for the depth data and Z.sub.g is the gain, or the extent to which the picture is dark.
When carrying out the dim effect, the switch 42 is switched to the terminal 43a so that the signal G.sub.Z is inputted to the multiplier 44. This G.sub.Z signal is then multiplied with the video signal S.sub.V inputted via the input terminal 45 (the multiplied signal is taken as being the signal S.sub.VG) . After this, the signal S.sub.VG, the key signal S.sub.K inputted via the input terminal 46 and the background signal S.sub.B are added together at the mixer 48, and a picture signal which constitutes the carrying out of the dimming effect is outputted via the output terminal 49.
When carrying out the fade effect, the switch 42 is switched to the terminal 43b so that the signal G.sub.Z is inputted to the multiplier 47. This G.sub.Z signal is then multiplied with the key signal S.sub.K inputted via the input terminal 46 (the multiplied signal is taken as being the signal S.sub.KG). After this, the signal S.sub.KG, the video signal S.sub.V inputted via the input terminal 45 and the background signal S.sub.B are added together at the mixer 48, and a picture signal which constitutes the carrying out of the fading effect is outputted via the output terminal 49.
The following problems were encountered when the dim and fade effects were carried out using the prior art circuit apparatus.
When carrying out the dim effect, as the signal G.sub.Z and the video signal S.sub.V are simply multiplied together at the multiplier 44, a certain amount of darkening will take place if the depth data for the picture has depth, but if the video signal S.sub.V is at zero when the signal G.sub.Z is at zero, the picture becomes completely black and the desired picture cannot be obtained.
In the same way, when carrying out the fading effect, as the signal G.sub.Z and the key signal S.sub.K are simply multiplied together at the multiplier 47, a certain amount of fading into the background will take place if the depth data for the picture has depth, but if the key signal S.sub.K is at zero when the signal G.sub.Z is at zero, the picture fades completely into the background and the desired picture cannot be obtained.
As the present invention is put forward as a result of the circumstances encountered in the prior art, while the dim effect is being carried out, when the above-described signal G.sub.Z is reflected on the video signal S.sub.V, the signal G.sub.Z is not simply multiplied with the video signal S.sub.V, but is instead mixed with a matt signal. Also, while the fade effect is being carried out, the signal G.sub.Z is not multiplied with the key signal S.sub.K to become one at the time of reflection, but is instead mixed with a fixed value signal.
It is therefore an object of the present invention to provide a special effects apparatus which, by carrying out the kind of mixing described above, can provide an extended dim effect and an extended fade effect where the dim effect does not become completely dark and the fade effect does not cause the picture to fade completely into the background.